In-situ Reaction Mechanism,Microstructure And Mechanical Properities Of SiC-Ti₃SiC₂ Composites

In this paper,submicron SiC-Ti₃SiC₂ composites of high SiC volume fraction were in-situ synthesized by hot isostaticlly pressing with the starting powders of SiC/TiH₂/C.X-ray diffraction（XRD）.Scanning electron microscope（SEM）、Transmission electron microscope（TEM）and First-Principle calculation were used to explore the in-situ reaction mechanism、densification mechanism and material composition.The main conclusions are as follow:The main phases of samples prepared in HIP-1600 ℃-100MPa-4h with the starting powders of β-SiC/TiH₂/C are β-SiC and TiC,little Ti₃SiC₂ was detected.But after Replacing the β-SiC powders with α-SiC powders,the SiC-Ti₃SiC₂ composites were successfully synthesized in the same process parameters and starting mixture of before,which suggested the SiC crystalline form have a great influence on the in-situ reaction of SiC/Ti/C starting powders and materials composition.First-principle calculation results shows that the average interface energy ofβSiC-TiC packed and non-packed interface are 3.81J/m2 and 4.37J/m2,which is lower than aSiC-TiC interface:4.03J/m2 and 6.32 J/m2.Due to the analogous crystal form and lattice parameters of βSiC and TiC,the βSiC-TiC interface have lower interface energy than aSiC-TiC interface system,which bring down the barrier of TiC formation and facilitate the TiC synthesis reaction,so that the in-situ reaction of Ti₃SiC₂ was restricted.High-resolution TEM results also indicate the pSiC-TiC interface is well-matched,which is consistent with the CASTEP calculation results.46vol.%SiC-Ti₃SiC₂、58vol.%SiC-Ti₃SiC₂ and 65vol.%SiC-Ti₃SiC₂ samples were synthesized via HIP in 1600℃-100MPa-4h,XRD and Micrographs show the a-SiC and Ti₃SiC₂ are main phase and all samples have a good density of 99.3%、98.5%and 97.3%,respectively.SEM results shows a uniform dispersion and good adhesion.The mechanical properties test results indicate the SiC-Ti₃SiC₂ composites have a high upgrade of fracture toughness and also maintained the high level of hardness of SiC ceramics.Fracture toughness and hardness of 46vol.%SiC-Ti₃SiC₂ samples is 6.2 MPa·m1/2 and 17.8GPa.With the increasing of SiC contents,the hardness increased while the bending strength and fracture toughness decreased slowly.SEM fracture analysis shows the crack energy could be consumed by crack separation and crack deflection,which improve the damage resistance and toughness of composite.